2.92 liters. According to relevant data, the average fuel consumption of 100 km is 7.3 liters, 0.073 liters for one km and 2.92 liters for 40 km. Automobile fuel consumption refers to the fuel economy index when the automobile is driving at a constant speed on a good road. Because constant speed driving is a basic working condition of automobile driving on the road, and this kind of fuel consumption is easy to measure, it is widely used.